This invention relates to a pressurizable tool adapted for expanding a sleeve firmly into a tube in a surrounding tubesheet. It relates particularly to such a tool device containing a pressurizable piston attached to an elastic expandable unit adapted for radially expanding the sleeve to provide a leak-tight seal between the sleeve and tube.
Tubes used in tubular type heat exchangers, particularly those used for air preheaters in fuel fired steam power plants, often develop leaks after several years service due to the corrosive action of the flue gases passing through the tubes, and metal erosion and/or fatigue and require repair or replacement. Such tube leaks are often located near the lower ends of the tubes adjacent a tubesheet. Because replacement of such tubes in a heat exchanger containing 10,000 to 50,000 tubes is quite expensive and requires considerable outage time for a plant, a special tool device and method has been needed for repairing such tubes quickly and economically in a dusty environment.
The prior art has disclosed various tool devices for remotely expanding tubes into tubesheets. For example, U.S. Pat. No. 2,319,216 to Dewald discloses a pull type tapered mandrel for expanding heat exchanger tubes into a tubesheet by utilizing direct contact between a tapered wedge surface and the tube inner wall to expand the tube. U.S. Pat. No. 4,068,372 to Kamohara et al discloses a tube expander for anchoring tubes in a tube plate of a heat exchanger, and utilizes a cylindrical shaped elastic medium to be expanded by axial compression utilizing a rod inserted through the medium and back up rings. U.S. Pat. No. 4,182,152 to Vaill et al discloses a grid sleeve bulge tool used for securing internal guide tools to an outer sleeve and grid. U.S. Pat. No. 4,387,507 to Kelly discloses apparatus and method for radially expanding tubes for anchoring within a tubesheet by using primary and secondary expander rings. U.S. Pat. No. 4,418,457 to Mueller discloses another apparatus for expanding a tube into a tubesheet opening and for controlling the tube expansion by axial location of elastomer washers relative to the tubesheet. Also, U.S. Pat. No. 4,567,631 to Kelly discloses another apparatus for expanding tubes into tubesheets using a plurality of elastomer expander rings loaded by axial compression. Furthermore, copending patent application, Ser. No. 833,624 filed Feb. 24, 1986 discloses a tube positioning tool and method which is generally related to the present invention. However, the prior art evidently does not disclose a pressurizable tool device adapted for conveniently and rapidly expanding a close-fitting metal sleeve firmly against a tube in a tubesheet, and which can withstand repeated cycles of use and can also be easily withdrawn from the expanded sleeve.
A special pressurizable tool and method has now been developed according to the present invention for repairing such leaking tubes by inserting a tubular metal sleeve into the tube, then inserting the tool into the sleeve and radially expanding the sleeve to seal the sleeve pressure-tight to the tube within the tubesheet. The tool utilizes multiple annular contoured elastomer expander rings which are axially compressed by a hydraulic piston means and exhibit long life during repeated high pressure usage of the tool.